Introduction
QR codes are data containers. Most people use them for website links. But they can hold much more. This guide explains exactly what you can put inside a QR code and how much space you have.
QR Code Data Capacity
A single standard QR code can hold a surprising amount of data. The maximum storage depends on the type of characters used:
- Numbers only: 7,089 characters
- Alphanumeric (Letters & Numbers): 4,296 characters
- Binary (Data/Bytes): 2,953 bytes
- Kanji/Kana: 1,817 characters
This is for the largest version (Version 40). Most codes you see in daily life are much smaller (Version 4-10) and hold fewer characters to keep them readable.
Common Data Types Included
You can store many different formats in a standard QR code:
1. Website URLs
This is the most common type. It stores a link like https://example.com. Scanning it opens the page in your browser.
2. Plain Text
You can store a simple message. Scanners simply display the text. No internet connection is needed to read it. This is useful for serial numbers or hidden notes.
3. vCard (Contact Info)
This acts like a digital business card. It organizes data into fields:
- Name
- Phone Number
- Email Address
- Mailing Address
- Website
When you scan a vCard QR code, your phone will ask to "Add to Contacts" automatically.
4. WiFi Credentials
This is very popular for cafes and guests. The code stores:
- SSID: The network name
- Password: The complicated wifi password
- Encryption: Usually WPA or WPA2
Scanning this connects your device to the WiFi instantly. No typing required.
5. Email and SMS
You can create a code that opens a pre-composed message.
- Email: Opens your mail app with the "To", "Subject", and "Body" filled in.
- SMS: Opens your text app with the destination number and message ready to send.
6. Calendar Events (iCal)
Stores meeting details like Title, Start Time, End Time, and Location. Scanning adds the event to your phone's calendar.
Error Correction Levels
QR codes have a built-in backup system called Error Correction (EC). This allows them to be scanned even if part of the code is damaged or covered.
- Level L (Low - 7%): Can restore 7% of data. Uses the least space. Best for printing small codes.
- Level M (Medium - 15%): The standard level for most uses.
- Level Q (Quartile - 25%): Good reliability.
- Level H (High - 30%): Can recover 30% of data. Best if the code will be outside, dirty, or if you want to put a logo in the middle.
Note: Higher error correction requires more dots (modules), making the QR code denser and potentially harder to scan at small sizes.
Static vs. Dynamic Storage
Static Codes: The data is stored directly in the pattern. If you change a single letter, the pattern changes. You cannot edit it after printing.
Dynamic Codes: The code stores a short link (e.g., qr.co/abc). This link redirects to your actual content. You can change the destination URL anytime without reprinting the code.
Security Risks
Because humans cannot read QR codes, you cannot see what is stored until you scan it. Malicious codes can:
- Send you to a fake banking site (Phishing)
- Connect you to a rogue WiFi network
- Trigger a premium SMS message
Always use a scanner that previews the data before performing the action.
Summary
QR codes are versatile tools. They can store URLs, contacts, WiFi passwords, and more. Understanding the limits of capacity and error correction helps you create better, more reliable codes.